特厚煤层孤岛煤柱水力扩孔防冲卸压技术研究

Hydraulic reaming technology for anti-burst and pressure relief of isolated coal pillar in extra-thick coal seam

砚北煤矿2502采区大巷保护煤柱两侧采空,为孤岛煤柱,应力集中程度高,由于煤层较厚,传统大直径钻孔卸压无法取得较好的防冲效果,针对该问题,提出了煤层水力扩孔卸压的技术。通过理论分析研究了水射流破煤和扩孔的卸压机理,水力扩孔通过增加钻孔孔径扩大了单孔的卸压范围;确定了砚北煤矿特厚煤层水力扩孔的主要技术参数,采用数值模拟分析了钻孔内分段扩孔的卸压模式;开发了相应的配套设备,采用双层高压钻杆实现煤体的“钻-割”一体化卸压,提高了卸压效率。通过砚北煤矿现场试验表明,煤层水力扩孔在水压40 MPa和高压喷嘴作用下,扩孔半径能够达到0.35~0.5 m,钻屑量在扩孔区域明显降低,表明水力扩孔能够显著降低煤体内应力集中,达到冲击地压防治的目的。

The main roadway in the 2502 mining area of Yanbei Coal Mine is an isolated island coal pillar with high stress concentration.Due to the large thickness of the coal seam,large diameter drilling for pressure relief cannot achieve good antiburst effect.To address this issue,a technical method for hydraulic reaming and pressure relief in coal seams was proposed.Through theoretical analysis,the pressure relief mechanism of water jet coal breaking and hole reaming was studied,and the main technical parameters of hydraulic hole reaming were determined.The pressure relief mode of segmented hole expansion in the borehole was analyzed using numerical simulation,and corresponding supporting equipment was developed and on-site tests were conducted.The results show that,hydraulic reaming expands the pressure relief range of a single hole by increasing the drilling diameter.The use of double-layer high-pressure drill pipes can achieve integrated pressure relief of coal drilling and cutting,improving pressure relief efficiency.The on-site test results show that when the water pressure of coal seam hydraulic expansion is 40 MPa and different nozzle combinations are used,the expansion radius can reach 0.35~0.5 m,and the amount of drilling debris in the expansion area is significantly reduced.The results indicate that hydraulic expansion can significantly reduce stress concentration in the coal body,achieving the goal of rock burst prevention and control.